Adaptive redundancy in three dimensional memory

摘要

In a three-dimensional nonvolatile memory, physical layers are zoned according to expected error rate. Different redundancy schemes are applied to different zones so that a high degree of redundancy is applied to a zone with a high expected error rate and a low degree of redundancy is applied to a zone with a low expected error rate.

主权项

1. A method of operating a three-dimensional nonvolatile memory that is monolithically formed in a plurality of physical levels of memory cells disposed above a substrate, memory cells in the plurality of physical levels connected in series to foim vertical NAND strings, comprising:
categorizing the plurality of physical levels into at least a first category of physical levels and a second category of physical levels according to expected error rate, the first category of physical levels having a first expected error rate, the second category of physical levels having a second expected error rate that is less than the first expected error rate; performing a redundancy calculation for data in the first category of physical levels, across N blocks of the three-dimensional nonvolatile memory, to generate first redundant data; storing the first redundant data in a redundant block in the three-dimensional nonvolatile memory; performing a redundancy calculation for data in the second category of physical levels, across N+X blocks of the three-dimensional nonvolatile memory, to generate second redundant data; and storing the second redundant data in the redundant block.